Prometheus plugin

Provides a Prometheus exporter to pass on Ceph performance counters from the collection point in ceph-mgr. Ceph-mgr receives MMgrReport messages from all MgrClient processes (mons and OSDs, for instance) with performance counter schema data and actual counter data, and keeps a circular buffer of the last N samples. This plugin creates an HTTP endpoint (like all Prometheus exporters) and retrieves the latest sample of every counter when polled (or “scraped” in Prometheus terminology). The HTTP path and query parameters are ignored; all extant counters for all reporting entities are returned in text exposition format. (See the Prometheus documentation.)

Enabling

The prometheus module is enabled with:

ceph mgr module enable prometheus

Configuration

By default the module will accept HTTP requests on port 9283 on all IPv4 and IPv6 addresses on the host. The port and listen address are both configurable with ceph config-key set, with keys mgr/prometheus/server_addr and mgr/prometheus/server_port. This port is registered with Prometheus’s registry.

Notes

Counters and gauges are exported; currently histograms and long-running averages are not. It’s possible that Ceph’s 2-D histograms could be reduced to two separate 1-D histograms, and that long-running averages could be exported as Prometheus’ Summary type.

The names of the stats are exactly as Ceph names them, with illegal characters . and - translated to _. There is one label applied, daemon, and its value is the daemon.id for the daemon in question (e.g. {daemon=mon.hosta} or {daemon=osd.11}).

Timestamps, as with many Prometheus exporters, are established by the server’s scrape time (Prometheus expects that it is polling the actual counter process synchronously). It is possible to supply a timestamp along with the stat report, but the Prometheus team strongly advises against this. This means that timestamps will be delayed by an unpredictable amount; it’s not clear if this will be problematic, but it’s worth knowing about.